As one of examples, US2004-0026975 (a first reference) discloses a motor vehicle seat that is known as this type of seat slide apparatus. In this motor vehicle seat, an upper rail secured to a seat is relatively movably mounted on a lower rail fixed on a vehicle body such as a vehicle floor. A lock unit, which incorporates, therein, plural lock pins and lock springs, is fixedly attached onto the upper rail. Plural engagement bores are formed at an undersurface of the lower rail, the plural engagement bores which are operatively engaged with the plural lock pins for the purpose of restraining or locking a longitudinal movement of the upper rail relative to the lower rail. When at least one of the plural lock pins is selectively engaged, in response to a longitudinal position of the upper rail relative to the lower rail, with the corresponding one of the plural engagement bores of the lower rail, it is possible to adjust finely a relative position of the upper rail relative to the lower rail, i.e., a position of the seat relative to the vehicle body such as the vehicle floor.
As another example, JPS57(1982)-194121A1 (a second reference, corresponding to U.S. Pat. No. 4,817,904A) discloses a seat slide apparatus for a vehicle that is known as this type of seat slide apparatus. In this seat slide apparatus, an upper rail secured to a seat is operatively mounted on a lower rail and is movable relative to the lower rail via rollers secured to the lower rail by retainers. The lower rail is provided with longitudinally extending series of holes at a side wall thereof. The seat slide apparatus is further provided with a lock member (described as a latch member in this reference) which is normally biased sidewise to be engaged with the holes of the lower rail. The upper rail is associated with this lock mechanism via an operation lever. That is, when the lock mechanism is moved rearward on the lower rail in response to operation of the operation lever, the engagement between the lock member and the holes of the lower rail is released so that the upper rail becomes movable relative to the lower rail.
As still another example, JP2002-160554A (a third reference) discloses a seat track device for a vehicle seat that is known as this type of seat slide apparatus. In this seat track device, attention is focused on reducing a degree of sliding friction applied to retainers, the sliding friction which may occur due to relative movement of an upper rail relative to a lower rail, and on stabilizing a degree of sliding friction applied thereto. Although the retainers include a changed structure in the light of the foregoing, the other configuration of the device is substantially identical to the one disclosed in the second reference. This seat track device is provided with a lock member (described as a lock lever in this reference) for restraining or locking a longitudinal movement of the upper rail relative to the lower rail, and are operatively engaged with lock holes formed at both the upper rail and the lower rail.
However, according to the motor vehicle seat disclosed in the first reference; a mechanism, by which the lock pins are engaged with the engagement bores (i.e., a lock unit), incorporates a great number of components therein. Therefore, it may undesirably results in requirement of a sufficiently large space for accommodating the lock unit. In such circumstances, it is difficult to downsize the mechanism.
According to the seat slide apparatus disclosed in the second reference, the lock member, which is mounted outside of the lower rail and the upper rail, causes greatening an entire structure of the seat slide apparatus. In such circumstances, it is difficult to downsize. Moreover, because the holes to be engaged by the lock member are formed only at the lower rail, it may be difficult to exert a sufficient degree of shear strength during a rail lock condition. For example, in the event that a vehicle is subjected to an unexpectedly large load, such as at a vehicle impact, it may cause a deformation in the lock member. Consequently, the lock member cannot exert a sufficient degree of locking strength.
According to the seat track device in the third reference, because the lock holes, which are engaged with the lock member, are formed at both the upper rail and the lower rail, a degree of locking strength can be enhanced. Meanwhile, because the retainers are attached on the same surface in which an operation position of the lock mechanism appears, the retainers are required to assure a longitudinal length that corresponds to a longitudinal operation length of the lock member. It may hence undesirably elongate a longitudinal length of the retainers. Moreover, likewise as the second reference, the lock member is mounted outside of the lower rail and the upper rail. Therefore, a difficulty in downsizing still remains.
The present invention has been made in view of the above circumstances, and provides a seat slide apparatus for use in a vehicle, which can adjust finely a position of a seat and is further downsized.